Doug Gregor wrote:
On Jan 10, 2008, at 3:40 PM, Michael Fawcett wrote:
My questions are - when creating your own library, when do you choose nested typedefs over a traits class,
Never.
and what effects does it have on a library user, both from a usability and extensibility point of view. What questions do you ask yourself to come to a decision?
Traits classes are far better than nested typedefs, because one can always specialize a traits class for an existing type---even if you can't modify the type because it is built-in or comes from another library that you can't modify.
Type members are inherited by derived classes -- traits specializations are not. So I don't think it's generally true that either one is better than the other -- it depends on what you're trying to achieve. Regards, Tobias